Last week, MPs voted for an amendment tabled by Conservative grandee Sir Graham Brady – and backed by the PM – which “requires the Northern Ireland backstop to be replaced with alternative arrangements to avoid a hard border”.

Many fear the “temporary single customs territory” created under the backstop plan would keep Britain tied to EU rules in the long term.

Downing Street has insisted the government is still considering alternatives.

What are the alternatives?

MPs have been looking at “alternative arrangements” to the backstop, which Mrs May has said she will discuss with EU leaders. They include:

a “trusted trader” scheme to avoid physical checks on goods flowing through the border

“mutual recognition” of rules with the EU

“technological” solutions

The UK is due to leave the EU at 23:00 GMT on Friday 29 March, when the two-year limit on withdrawal negotiations enforced by the Article 50 process expires.

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If MPs approve a deal with Brussels, the parties will then have until the end of 2020 to negotiate a future trade deal. If that is not in place by the end of this transition period, the backstop kicks in.

Without a deal, however, there would be no backstop and no transition period.

The prime minister has said she is “determined” to deliver Brexit on time, but a number of cabinet ministers have indicated they would be willing to agree to a short extension to finalise legislation for Brexit.

Who is the PM meeting on Wednesday?

Mrs May will head to Stormont House to have bilateral meetings with Stormont’s five biggest political parties:

The Democratic Unionist Party (DUP) – the Conservative Party’s confidence-and-supply partner at Westminster

Sinn Féin

SDLP

Ulster Unionist Party (UUP)

Alliance Party

Two deadlocks are likely to be on the agenda: Brexit and the lack of a Northern Ireland Assembly.

PAUL FAITHStormont’s institutions have been deadlocked since power sharing collapsed more than two years ago

There has been no functioning devolved Northern Ireland government since January 2017, after a row between the DUP and Sinn Féin collapsed the power-sharing executive.

For almost 10 years before that, the DUP and Sinn Féin worked together in government under a system of mandatory coalition, where unionist and nationalist parties shared power.

The government collapsed after Sinn Féin’s Martin McGuinness resigned as deputy first minister, citing the DUP’s conduct around a flawed energy scheme, the Renewable Heat Incentive (RHI).

It sparked a snap election, but since then, various talks processes have collapsed and the Northern Ireland Secretary Karen Bradley had to take control of financial matters and pass its budget bills through Westminster.

Theresa May will hold Brexit talks with Northern Ireland’s five main political parties at Stormont later. The PM is on a two-day visit to try to reassure people she can secure a Brexit deal that avoids the return of customs checkpoints on the Irish border.